Device Shots - Generate high-resolution device mockups using a screenshot.
shotsnapp - Create beautiful device mockup presentation
Mockuuups Studio - Fast and easy way to create product mockups on macOS, Windows and Linux.
Base UI Sketch Framework - Huge set of everything you need to design and prototype
Screen Size Map - An interactive map of screen sizes for responsive web design
Sketchapp TV - Create Awesome iOS Apps With Sketch